TITLE:   GCN CIRCULAR
NUMBER:  32693
SUBJECT: GRB 221009A: LCOGT Optical Afterglow Detection
DATE:    22/10/11 17:04:03 GMT
FROM:    Robert Strausbaugh at University of Minnesota  <rstrausb@umn.edu>

R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:

We observed the GRB 221009A/Swift J1913.1+1946 (Dichiara et al., GCN 32632)
field with the LCOGT 1-meter Sinistro instrument at the Teide Observatory,
on Tenerife, on October 10, from 19:33 to 19:50 (corresponding to 29.38 to
29.66 hours from the GRB trigger time) with the SDSS g, r and i filters.

We performed a series of 3x100s exposures in each band.  We clearly detect
the optical transient at the UVOT coordinates (Dichiara et al., GCN 32632),
in r and i bands, and marginally in g-band (2-sigma detection), consistent
with other optical detections.

The following magnitudes are calculated using the Pan-STARRS catalog as
reference:

g = 20.87 +/- 0.36
r = 18.80 +/- 0.21
i = 17.77 +/- 0.20

These magnitudes are not corrected for galactic extinction.  Further
observations are planned.